Field of the Invention
The present invention relates to stabilization control for images formed by image forming apparatuses.
Description of the Related Art
Color reproducibility is important for image forming apparatuses. In order to improve color reproducibility, US 2006/198648 discloses a configuration in which the density of an image formed on a sheet is detected by a reader unit in an image forming apparatus, which is a copying machine, and image forming conditions are controlled. US 2006/198648 discloses a configuration in which an RGB sensor is provided in the image forming apparatus, and an image formed on a sheet is read by the RGB sensor to control the image forming conditions. Furthermore, US 2004/042807 discloses a configuration in which image forming conditions are controlled using a spectral reflectance sensor, which has a wider reading area and higher accuracy than those of an RGB sensor. The configurations described in US 2006/198648 and US 2004/042807 are for detecting an image formed on a sheet while conveying the sheet in the image forming apparatus. However, if a sheet that is being conveyed flaps, reflected light from the sheet varies and the adjustment accuracy of the image forming conditions is affected. Japanese Patent Laid-Open No. 11-11718 discloses an image forming apparatus that has a detection unit for detecting flapping of a sheet.
With the configuration described in Japanese Patent Laid-Open No. 11-11718, a space for providing the detection unit for detecting flapping of a sheet is required, and moreover, the provision of this detection unit increases cost. Furthermore, when performing colorimetric measurement on an image on a sheet that is being conveyed, not only flapping of the sheet but also unevenness in the sheet conveyance speed affect the measurement accuracy. For example, if, at a colorimetric measurement timing for an image, colorimetric measurement is performed on a part of the previous image or the next image due to the unevenness in the conveyance speed, a difference in tone called a tone jump occurs under an image forming condition that is based on the result of this colorimetric measurement. Moreover, in the case of performing colorimetric measurement on a large number of colors in order to create a multi-color lookup table (LUT), colorimetric measurement needs to be performed on an image with more than 200 colors. The number of sensors needs to be increased to perform colorimetric measurement on an image with such a large number of colors, but in this case, a tone jump occurs due to a difference in reading accuracy among the sensors.